CT Lab scans challenge theories of ancient glass making

Scans from the CTLab in RSPE are challenging centuries-old theories on how ancient Roman cameo glass was made and suggest the British Museum's most famous Roman glasswork is wrongly classified.

The CTLab worked with Associate Professor Richard Whiteley from the ANU School of Art and Design to study air bubbles in Roman glass, revealing structure that are inconsistent with blown glass.

"There was a critical moment for me when I felt strongly that historians and archaeologists have been wrong for hundreds of years," Associate Professor Whiteley said.

Associate Professor Whiteley, who is known internationally for his glass artworks, said his research over the past decade indicated that Roman cameo glass is not blown glass, but was made by a cold-pressing process now known as pate de verre.

The research challenges conventional thinking about how glass was created in the period of around 30BC-50AD such as the Portland Vase, the British Museum's most famous example.

Researchers from the Research School of Physics and Engineering and the School of Art and Design studied a fragment of Roman cameo glass from the ANU Classics Department with a Computed Tomography scanner in the CT Lab.

The images for the first time revealed the shape, direction and composition of air bubbles trapped between a blue and white layer of Roman glass.

"I remember the moment I saw it, I said: Oh my god, this is extraordinary, because I also saw cold working marks in the surface which were inconsistent with the assumption that it was blown," Associate Professor Whiteley said.

He will present his new evidence at a historical glassworks conference at the British Museum this week.

"I carve and shape glass with my hands, and have done for decades. The marks I saw were inconsistent with what I see in my work.

"We saw a bubble configuration within the glass that results from a pressing and turning motion. I believe that cold granulated glass has been packed into a mould and then a blob of molten blue glass introduced and pressed against mould heating the white granules from behind.

"You just would not get a bubble that size and flat-shaped from blowing. The most striking thing about it, is not its size and its flatness, but we found a section where the blue glass has mixed with the granulated white specks of glass."

Associate Professor Whiteley acknowledges a German artist, Rosemarie Lierke, came to a similar conclusion in the 1990s, but her writings have not been accepted because of the lack of evidence.

Associate Professor Whiteley hopes his new theory will gain acceptance and funding for an international research team to recreate the Portland Vase using the original pate de verre method.

"It's not about proving people wrong, it's about correcting the historical record and reviving and restoring a technique lost for over 2,000 years."

Associate Professor Whiteley's findings have only been made possible through collaboration with Emeritus Professor Elizabeth Minchin at the ANU Classics Department, who allowed testing on a fragment of Roman Cameo glass, and the Research School of Physics and Engineering CTLab, in the Applied Maths Department.